Various purine derivatives are known including guanine derivatives having activity as inhibitors of purine nucleoside phosphoxylase (PNP-4) Ser. No. 767,202 filed Aug. 22, 1985, which is a continuation of U.S. Ser. No. 660,152 filed Oct. 12, 1984, now abandoned. Selected guanine derivatives previously known are also disclosed in the application. Therefore, U.S. Ser. No. 767,202, now U.S. Pat. No. 4,772,606 is incorporated herein by reference.
More specifically the following pyrrolo[3,2-d]pyrimidin-4-ones having the Formula ##STR1## are known. The compound of Formula 1 is disclosed in J. Org. Chem., 1979, 44:3826 and the compounds of Formula 2, 3, and 4 are disclosed by J. d. Stoeckler, et al., Cancer Res., 1986, 46:1774). Further, Stoeckler, et al disclose PNP activity for compounds of the Formula 2, 3, and 4. These compounds differ from the present invention by an aryl or heteroaryl substituent compared to the methyl in the compound of Formulae 1 and the sugar moiety in the compounds of Formula 2, 3, and 4. Thus, the present invention are compounds which are not obvious variants thereof.